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Grabby Aliens (2021)

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Re: Grabby Aliens (2021)

#71

Post by Mistletoe »

XorNot wrote: post #65
cryptonector wrote: post #63

Earlier quoted context omitted.

The speed of light is a tremendous limitation. W/o FTL there's no such thing as "loud alien civilizations" that can "control 40%-50% of [the] universe['s] volume".

Rather depends on other factors though: you can perfectly well run an interstellar empire with very long communication times and people going into suspended animation for transit. Control strategy simply has to adapt accordingly: i.e. a message probably comes with a fleet sufficient to ensure its obeyed. This was one of the ideas in the Doom novelizations: that the aliens had spent so long travelling that there was l…

Suspended animation may be as impossible as faster than light travel.

Re: Grabby Aliens (2021)

#72

Post by p1mrx »

cryptoz wrote: post #38
Charon77 wrote: post #32

Earlier quoted context omitted.

If a planet in the nearest star harbors life form that launched a rocket, would we know?

No, we wouldn't know today. But this is knowable in about 50 years or so, if we send probes to ~550AU and use the Sun as a gravitational lens; we will then be able to get high-res (1km resolution?) photos/videos of nearby extrasolar planets themselves. This may be enough to find a spacefaring civilization. (sure, rockets aren't 1km big, but they do leave big traces. maybe we could see that)

That seems like a good match for this nuclear sail concept:

https://www.nasa.gov/general/thin-film-isotope-nuclear-engin...

> The basic concept is to manufacture thin sheets of a radioactive isotope and directly use the momentum of its decay products to generate thrust.

Actually it's mentioned at the end of the article:

> Novel ability to reach deep space (> 150 AU) very quickly and then continue aggressive maneuvers (> 100 km/sec) for dim object search/rendezvous and/or retargeting telescopes at the solar gravitational focus over a period of years.

Re: Grabby Aliens (2021)

#73

Post by XorNot »

cwillu wrote: post #67
GavinB wrote: post #10

This is a compelling theory, especially the implication that humans are early. I do wonder whether we should see the evidence of spheres of growing alien influence out in the stars, but instead we see a highly uniform universe in all directions. This would indicate a few possibilities: 1. Expanding alien civilizations are relatively low impact and don't collect all of the energy of stars in ways that are visible to o…

Alas, there's a fifth possibility: 5. Controlled transportation between the stars, sufficient for colonization, is sufficiently impractical that there are no grabby aliens within our light-cone.

That itself would be quite interesting though, because based on what we know now it's merely difficult, not impossible with reasonably foreseeable technological improvements.

The dynamics which would make it impossible on any known timespan don't seem currently observable.

Re: Grabby Aliens (2021)

#74

Post by XorNot »

zarzavat wrote: post #70
actionfromafar wrote: post #6

Earlier quoted context omitted.

Barely spacefaring. We are like fish on the shore who can survive in the mud long enough for the tide to come back to rescue us, if that.

That’s just because our neighbourhood is so boring in comparison to Earth. Imagine that by some chance Mars was another Earth with a breathable atmosphere. NASA would have been given a trillion dollar budget and we would have been there in the 80s. Instead it’s a dead red rock so NASA gets a small budget and the US spends its money on blowing people up instead. We have the technology to be a spacefaring civilisation…

I do keep hoping we get lucky in my lifetime and a massive, water bearing comet with slam into Mars and jumpstart the terraforming.

Watching a planet which could retain water go from "nothing to oceans" would be amazing.

Re: Grabby Aliens (2021)

#75

Post by Animats »

XorNot wrote: post #65
cryptonector wrote: post #63

Earlier quoted context omitted.

The speed of light is a tremendous limitation. W/o FTL there's no such thing as "loud alien civilizations" that can "control 40%-50% of [the] universe['s] volume".

Rather depends on other factors though: you can perfectly well run an interstellar empire with very long communication times and people going into suspended animation for transit. Control strategy simply has to adapt accordingly: i.e. a message probably comes with a fleet sufficient to ensure its obeyed. This was one of the ideas in the Doom novelizations: that the aliens had spent so long travelling that there was l…

> Rather depends on other factors though: you can perfectly well run an interstellar empire with very long communication times and people going into suspended animation for transit.

Probably not. Historically, a few months of lag is roughly the upper limit for running an empire. The Roman empire got round trip lag down to two months to the distant provinces. The Spanish empire was at 4-5 months of lag for the New World. Holding an empire together with a lag of decades probably won' work.

Re: Grabby Aliens (2021)

#76

Post by tsimionescu »

bqmjjx0kac wrote: post #56
bhickey wrote: post #52

Earlier quoted context omitted.

What you're suggesting doesn't make sense. Dark matter isn't non-luminous matter. It's matter that only interacts gravitationally, but not electromagnetically. This means it doesn't undergo collisions and can't shed angular momentum. It forms a diffuse, largely uniform cloud throughout galaxies. The result is that galaxies are more dense further from the galactic core than we would predict from luminous matter alone.

I'm speaking outside my area, but dark matter is not really confirmed to even exist?

It's clearly confirmed that galaxies don't obey the known laws of quantum electrodynamics (QED) + general relativity (GR) if we assume they are made entirely of Standard Model particles. So, either QED is wrong (extremely unlikely) or GR is wrong (unlikely) or there is some matter that is not in the Standard Model (plausible).

Dark matter corresponds to option 3 - and there are observations that conform some models of dark matter distribution that match quite well between different galaxies. There are other theories as well, such as MOND (modified Newtonian gravity) that explore option 2 (GR is wrong).

Still, whatever the theory, it's clear that what is not happening is "aliens someone consuming all of the EM radiation from some stars". With anything resembling currently known physics, it's impossible to "consume" EM radiation in this way. Electric charge is always conserved, electrons and quarks don't disappear just because they move around, even with something like controlled fusion. A Dyson sphere would be an extremely hot visible object, not some dark point.

Re: Grabby Aliens (2021)

#77

Post by lostemptations5 »

XorNot wrote: post #74
zarzavat wrote: post #70

Earlier quoted context omitted.

That’s just because our neighbourhood is so boring in comparison to Earth. Imagine that by some chance Mars was another Earth with a breathable atmosphere. NASA would have been given a trillion dollar budget and we would have been there in the 80s. Instead it’s a dead red rock so NASA gets a small budget and the US spends its money on blowing people up instead. We have the technology to be a spacefaring civilisation…

I do keep hoping we get lucky in my lifetime and a massive, water bearing comet with slam into Mars and jumpstart the terraforming. Watching a planet which could retain water go from "nothing to oceans" would be amazing.

Evidence suggests Mars had oceans before and they just evaporated due to the thin atmosphere and non-existant magnetic field no?

I'm not sure how that would get solved without some active technological solution by humans let's say.

Re: Grabby Aliens (2021)

#78

Post by cryptonector »

cwillu wrote: post #66
cryptonector wrote: post #63

Earlier quoted context omitted.

The speed of light is a tremendous limitation. W/o FTL there's no such thing as "loud alien civilizations" that can "control 40%-50% of [the] universe['s] volume".

As stated in the paper: “The second of our three model parameters is the (assumed universal) speed at which grabby civilizations expand. Our model predicts that on average at grabby origin dates, a third to a half of the universe is within grabby-controlled volumes. So if the grabby expansion speed were low, many such volumes should appear quite large and noticeable in our sky. However, as noted by (Olson ’15; Olsen…

They couldn't be cohesive civilizations though, not unless their individual lifetimes were very long.

Re: Grabby Aliens (2021)

#79

Post by cryptonector »

XorNot wrote: post #65
cryptonector wrote: post #63

Earlier quoted context omitted.

The speed of light is a tremendous limitation. W/o FTL there's no such thing as "loud alien civilizations" that can "control 40%-50% of [the] universe['s] volume".

Rather depends on other factors though: you can perfectly well run an interstellar empire with very long communication times and people going into suspended animation for transit. Control strategy simply has to adapt accordingly: i.e. a message probably comes with a fleet sufficient to ensure its obeyed. This was one of the ideas in the Doom novelizations: that the aliens had spent so long travelling that there was l…

> you can perfectly well run an interstellar empire with very long communication times and people going into suspended animation for transit.

If travel times are orders of magnitude longer than lifetimes, then you will tend to lose civilizational cohesion.

> Control strategy simply has to adapt accordingly: i.e. a message probably comes with a fleet sufficient to ensure its obeyed.

What even is the point? The message takes N years to be received by a receiver N light-years away, but travel times will be orders of magnitude longer, so no "fleet" can be sent.

Re: Grabby Aliens (2021)

#80

Post by lostemptations5 »

hotpotamus wrote: post #29
echelon wrote: post #7

Earlier quoted context omitted.

> implication that humans are possibly one of the earliest sentient spacefaring species to have appeared so far. Or that perhaps we're a simulation. We exist in a very interesting time in history when the pieces are coming together. Our hypothetical future robot descendents may be very interested in learning about their past.

If we're in a simulation, there's no reason that other beings couldn't have also arisen within the simulation with us.

Or that they are also in a simulation.
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